U.S. Pat. No. 5,270,252 to Papanicolaou is a Schottky diode on beta silicone carbide. The metals taught in the Papanicolaou disclosure are platinum, tungsten, titanium tungsten, gold and aluminum. The Schottky diode of the Papanicolaou disclosure is used for high temperature semiconductor applications and, in particular, it is used as a rectifying diode.
U.S. Pat. No. 5,612,232 to Thero, et al. is a Schottky diode for use in high temperature applications but it cannot be used as a gas sensor. Thero, et al. teaches the use of a silicon carbide semiconductor with nickel and tungsten as metals.
U.S. Pat. No. 4,622,736 to Drobny discloses Schottky diodes for use in connection with a silicon semiconductor. Tungsten, titanium-tungsten, and vanadium are the metals used in the invention. The Drobny Schottky diode is not a gas sensor.
The development of a Schottky diode structure has been reported by the researchers at Linkoping University. The structure of the Linkoping sensor is Pt on TaSix on SiO2 on SiC. The Pt/TaSix/SiO2 thicknesses are 100 nm/10 nm/5 nm respectively. The sensor responses are stable and fast but they are not highly sensitive.